Detonator utilizing features of automotive airbag initiators

ABSTRACT

A detonator that incorporates certain features of automotive airbag initiators, and methods of making same.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to pyrotechnic detonators, and more particularly, to a detonator that incorporates features known in certain automotive airbag initiators.

[0002] The efficient use of explosives in mining operations and the demolition of structures often requires that many charges be placed in a predetermined pattern and detonated in a timed sequence. In general, timed detonation can be accomplished by detonators that use pyrotechnic delays, sequential-type blasting machines, and electronically programmable detonators. Some examples of time-delayed detonators are described in U.S. Pat. Nos. 6,173,651, 6,085,659, 6,079,332, 5,602,360, 5,460,093, 5,435,248, 4,869,170, 4,819,560, 4,730,558, and 4,712,477, the disclosures of which are hereby incorporated by reference herein.

[0003] Such detonators are subject to one or more drawbacks, however, such as the following: (1) the use of an ignition element that is difficult to manufacture to precise dimensions so as to ensure predictable performance, (2) the use of an ignition element that requires careful handling during manufacturing and thus impedes the beneficial incorporation of automated steps in the detonator assembly process, (3) the use of an ignition charge that contains lead, which presents an environmental and health hazard, (4) the use of a non-low energy ignition element, which reduces the ability to provide a compact design, (5) lack of reliability, and (6) costly manufacturing.

[0004] On the other hand, such problems are overcome or at least ameliorated in well-known automotive airbag initiators such as those currently manufactured and sold by the assignee of this patent application. Various patents also disclose other examples of initiators having features that address one or more of such problems, including U.S. Pat. Nos. 6,274,252, 5,709,724, 5,639,986, 5,602,359, 5,596,163, 5,404,263, 5,140,906, and 3,971,320, the disclosures of which are hereby incorporated by reference herein.

[0005] Despite the advances regarding these issues in the automotive airbag initiator field, it is believed that hitherto it has not been conceived or attempted to apply various features of such automotive initiators that overcome or ameliorate the aforementioned problems, to detonators that are used in mining, blasting, and demolition.

SUMMARY OF THE INVENTION

[0006] One object of the present invention is to provide a detonator that incorporates one or more features of automotive airbag initiators so as to overcome or ameliorate one or more of the problems enumerated above.

[0007] Another objective of the present invention is to provide a detonator utilizing an ignition element similar to those in automotive initiators, resulting in a reliable and economical detonator.

[0008] Another separate and alternative objective of the present invention is to provide a detonator utilizing an ignition element that is relatively easy to manufacture to precise dimensions with known and proven manufacturing processes, resulting in a detonator having predictable performance.

[0009] It is another separate and alternative objective of the present invention to provide a detonator utilizing an ignition element that is sufficiently durable to permit the incorporation of useful automation steps in the detonator assembly process.

[0010] It is a further separate and alternative objective of the present invention to provide a detonator utilizing an ignition charge that does not contain any lead, so as to reduce hazards to the environmental and health resulting from the use of the detonator.

[0011] It is yet another separate and alternative objective of the present invention to provide a detonator utilizing a low energy ignition element, resulting in a detonator that may be made more compact.

BRIEF DESCRIPTION OF THE FIGURES

[0012]FIG. 1 is a side sectional view of an embodiment of the present invention, showing the ignition subassembly portion of the detonator.

[0013]FIG. 2 is a top sectional view of an alternate ignition subassembly embodiment to that of FIG. 1.

[0014]FIG. 3 is a partial exploded and sectional view showing how an ignition subassembly such as that of FIG. 1 fits into a loaded shell of a detonator according to the present invention.

[0015]FIG. 4 is partial top sectional view of the header and part of the circuit board of the ignition subassembly of FIG. 2.

[0016]FIG. 5 is a partial bottom view of the header and part of the circuit board shown in FIG. 4, illustrating the offset from centerline of the header's pins.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT¹

[0017] Referring to FIGS. 1 and 2, an ignition subassembly 8 of an embodiment of the present invention, and an alternate embodiment 8′, are shown. As shown in FIG. 3, such a subassembly is placed inside of a shell 40 that may contain a primary charge 36 and a base charge 38 loaded into its closed end. (A detonator shell is typically a metal cylinder 6 to 8 mm. in diameter and from 60-100 mm. in length). Subassembly 8 can then be secured in place in the shell 40, such as by placing an elastomeric plug or the like (not shown) in the open end of the shell and crimping the shell 40 to the plug, or other suitable method. Subassembly 8 may have a body portion 32 formed of an encapsulation 31 and may have ridges 57 protruding out from the outer surface of body portion 32, so as to snugly hold subassembly 8 within the shell 40. Such ridges 57 or other protuberances may preferably be formed to dampen vibrations to which the detonator may be subjected, generally in accordance with the teachings of U.S. Pat. No. 6,079,332.

[0018] Alternately, an ignition subassembly similar to that of FIGS. 1 and 2 (but preferably lacking encapsulation 31) can be directly incorporated into a shell, such as by molding it directly in the shell. Various other methods of incorporating an ignition element into a detonator in accordance with the present invention will be readily apparent, and it is noted that implementing various automotive airbag initiator features in a detonator according to the present invention does not require the use of a “standalone” ignition subassembly like the ones shown in FIGS. 1-3.

[0019] Turning to the specifics of the automotive airbag initiator features incorporated in the depicted embodiments, it can be seen that an automotive airbag initiator-style ignition element 28 is provided at one end of the ignition subassembly 8. Specifically, ignition element 28 includes a header assembly with a sealed electrical feedthrough, comprising an eyelet 10 (preferably stainless steel), insulator glass 14 (preferably a glass such as a sodasilicate, e.g., 9010, that is chosen to form a compression seal with the eyelet and center pin, or less preferably a matched seal), a center pin 18 (preferably an iron/nickel alloy), a ground pin 20, and an igniter wire 12 (preferably a low energy igniter wire with a diameter of 10 to 20 microns). Ground pin 20 and center pin 18 are preferably selected of the same material. The ignition element 28 further preferably includes a charge can 26 that is preferably metallic and hermetically sealed to the eyelet at circumferential through-weld 16, with an ignition charge 30 contained between the can 26 and upper surface of the header, in tight contact with igniter wire 12. An insulator cup 27 may preferably be attached around the can 26 so that, except for female connectors 52 that protrude from the input end of the subassembly, the entire outer surface of ignition subassembly 8 consists of insulating material, thus providing electrical isolation and vibration and environmental protection to the components within.

[0020] In the depicted embodiment, a circuit board 24 and electronic components 25 may be provided within ignition subassembly 8, to provide a means of triggering ignition of the ignition element based on the processing of an electrical ignition signal received by input leads 51, which are electrically connected to a blasting machine or the like that powers the detonator. Such electronic components are well-known and preferably include means for imparting a programmable period of delay to the ignition, means for ESD and RF protection, et cetera. (Another preferred alternative is the use of an application-specific integrated circuit). Circuit board 24 and electronic components 25 are preferably encapsulated together in encapsulation 31, and connected to pins 18 and 20 at contacts 22 through soldering or other suitable connection. Referring to FIGS. 2 and 4, as is well-known in encapsulated automotive airbag initiators, retention of the ignition element 28 to the encapsulation 31 may be enhanced by providing a lip 17 at the bottom of the eyelet 10′. The insulator cup 27′ may also be held within the encapsulation to facilitate its retention as well.

[0021]FIGS. 4 and 5 illustrate an alternate embodiment similar to that of FIG. 2, wherein the pins 18′ and 20′ are slightly offset from the centerline of the header, so that the circuit board 24 can occupy that centerline, which corresponds to the widest portion of the cylindrical body portion 32.

[0022] By way of example, in an embodiment like that shown in FIGS. 1 and 2, it has been found that a nickel/chromium alloy, 13 micron diameter, 0.7 mm long igniter wire, a 50 mg ignition charge of zirconium potassium perchlorate having a height of 1.0 mm and a diameter of 4.8 mm is suitable. Preferably, a minimum suitable charge is approximately 30 mg for a configuration of this size, as a smaller charge may result in an insufficient charge thickness. A preferred all-fire voltage may be 6 volts, and may be delivered with a 100 microfarad capacitor included in the electronic components 25 in an embodiment like that depicted.

[0023] It should be noted that although the Figures depict embodiments including electronic components that receive, process, and deliver an ignition signal, such an ignition signal may alternately be received, processed, and delivered by a number of other well-known non-electronic or partly-electronic means, such as through the use of a shock tube to deliver an ignition signal to a piezoelectric device, column fuse delays, et cetera. It is noted that this detailed description of certain embodiments does not imply that such alternate embodiments are not within the scope of the invention.

[0024] A preferred embodiment of a detonator utilizing features known in certain automotive airbag initiators, and many of its attendant advantages, has thus been disclosed. It will be apparent, however, that various changes may be made in the form, construction, and arrangement of the parts without departing from the spirit and scope of the invention, the form hereinbefore described being merely a preferred or exemplary embodiment thereof. Therefore, the invention is not to be restricted or limited except in accordance with the following claims. 

What is claimed is:
 1. A detonator comprising: a) a cylindrical shell having a detonator end and an input end, said detonator end being closed and packed with a charge; b) an ignition element within said shell and located adjacent to said charge, said ignition element including one or more of the following: i) a header including a sealed feedthrough, ii) a metallic charge can, iii) an electrically insulating cup, iv) a zirconium potassium perchlorate ignition charge, v) a low-energy igniter wire; and, c) trigger means extending from said input end of said shell to said ignition element, for causing said ignition element to ignite in response to the receipt of a selected signal by said trigger means.
 2. The detonator of claim 1, wherein said trigger means includes two electrical input leads at said input end of said shell.
 3. The detonator of claim 1, wherein said trigger means includes a delay means for delaying the ignition of said ignition means for a predetermined period of time after receipt of said selected signal by said trigger means.
 4. The detonator of claim 3, wherein said delay means is an electronic delay means.
 5. The detonator of claim 1, wherein said shell has a thickness of 0.5 mm, and an outer diameter of between 6 mm and 8 mm.
 6. A detonator comprising: a) a cylindrical shell having a detonator end and an input end, said detonator end being closed and packed with a charge; b) an ignition element within said shell and located adjacent to said charge, said ignition element including a header with a sealed feedthrough; and, c) a trigger means extending from said input end of said shell to said ignition element, for causing said ignition element to ignite in response to the receipt of a selected signal by said trigger means.
 7. The detonator of claim 6, wherein said ignition element includes an ignition charge, a can surrounding said ignition charge and connected to said header, and an insulating cup surrounding said can.
 8. The detonator of claim 6, wherein said ignition element includes an ignition charge that includes zirconium potassium perchlorate.
 9. The detonator of claim 6, wherein said ignition element includes a low-energy igniter wire having two ends that are electrically connected to said feedthrough.
 10. The detonator of claim 9, wherein the diameter of said igniter wire is less than 20 microns.
 11. The detonator of claim 6, wherein said header includes a glass-to-metal seal.
 12. The detonator of claim 11, wherein said header is an all-glass header.
 13. The detonator of claim 6, wherein said shell has a thickness of 0.5 mm, and an outer diameter of between 6 mm and 8 mm.
 14. The detonator of claim 6, wherein said trigger means includes two electrical input leads at said input end of said shell.
 15. The detonator of claim 6, wherein said trigger means includes a delay means for delaying the ignition of said ignition means for a predetermined period of time after receipt of said selected signal by said trigger means.
 16. The detonator of claim 15, wherein said delay means is an electronic delay means.
 17. A method of making a detonator comprising the following steps: a) providing a cylindrical shell having a detonator end and an input end, said detonator end being closed; b) packing said detonator end of said shell with a suitable charge; c) providing an ignition element including a header with a sealed feedthrough within said shell and adjacent to said charge; d) providing a trigger means extending from said input end o f said shell to said ignition element, said trigger means for causing said ignition element to ignite in response to the receipt of a selected signal by said trigger means; and, e) securing said ignition element and trigger means within said shell.
 18. The method of claim 17, further comprising the step of loading an ignition charge of zirconium potassium perchlorate within said ignition element.
 19. The method of claim 17, further comprising the steps of: providing a metallic can and loading it with an ignition charge, securing said can to said header, and securing an insulating cup around said can.
 20. The method of claim 17, wherein said trigger means includes a delay means for delaying the ignition of said ignition means for a predetermined period of time after receipt of said selected signal by said trigger means. 